Telomeres do get shorter with age, the study confirms, but men older than 75 and women over age 80 tended to have longer telomeres than their slightly younger counterparts. That result does not mean that telomeres start to grow in length once people reach a certain age, Schaefer said. Rather, the finding probably means that people with shorter telomeres died before they reached those ripe old ages and the survivors are those that carry longer telomeres.

African-Americans tended to have longer telomeres than European-Americans, Latinos or Asians, the researchers found. The reason for that difference is not clear. As expected, people who smoked or drank heavily were more likely to have shorter telomeres, and higher levels of education were associated with longer telomeres. Other studies have linked exercise with longer telomeres, but Schaefer and her colleagues found no such association.

One of the study’s findings is rather puzzling, said Dan Eisenberg, an anthropologist at the University of Washington in Seattle who studies telomeres’ link to health, but who was not involved in the Kaiser Permanente study. Higher body mass index, or BMI, was associated with longer telomeres. The discovery is counterintuitive, Eisenberg said, because higher BMIs —those associated with being overweight or obese — are linked to a variety of health problems including diabetes and heart disease. Eisenberg said he would have expected telomeres in people with higher BMIs to be shorter.